The subject invention is directed toward the art of ladders and ladder-like devices and, more particularly, to improved ladder constructions which are formed from simple extruded and/or molded parts.
The invention will be described with respect to certain preferred embodiments; however, as will become apparent, the invention can be embodied in many forms of ladder-like structures.
In the past, many different materials have been used to form ladders. Most commonly, wood and aluminum have been the predominate ladder materials. The reasons for this are many; high strength to weight ratios, ease of forming the component parts, ease of assembly, good rigidity, etc.
Although plastic and various resins have been recognized as possessing desirable properties for ladder construction, to date attempts at forming ladders from them have not been particularly successful. Typical drawbacks to the successful use of plastics were high weight and fabrication problems. Additionally, although material costs were generally low, the cost of the ladders were not especially competitive because of the large and expensive dies and molds required.
A major portion of the problems involved with the prior unsuccessful use of plastics in ladder construction resulted from the fact that the designers merely adopted the same designs as were successfully used with aluminum or wood.